package com.xinxin.datastructure.map.impl;

import com.xinxin.datastructure.map.Map;

/**
 * @author ：史鑫鑫
 * @date ：Created in 2019/5/23 23:52
 */
public class BSTMap<K extends Comparable<K>, V> implements Map<K, V> {

    private class Node {
        K key;
        V value;
        Node left, right;

        Node(K key, V value) {
            this.key = key;
            this.value = value;
            left = null;
            right = null;
        }
    }

    private Node root;
    private int size;

    public BSTMap() {
        root = null;
        size = 0;
    }

    @Override
    public void add(K key, V value) {
        root = add(root, key, value);
    }

    private Node add(Node node, K key, V value) {
        if (node == null) {
            size++;
            return new Node(key, value);
        }
        if (key.compareTo(node.key) < 0) {
            node.left = add(node.left, key, value);
        } else if (key.compareTo(node.key) > 0) {
            node.right = add(node.right, key, value);
        } else {
            node.value = value;
        }
        return node;
    }

    @Override
    public V remove(K key) {
        Node node = getNode(root, key);
        if (node != null) {
            root = remove(root, key);
            return node.value;
        }
        return null;
    }

    // 删除掉以node为根的二分搜索树中值为e的节点，递归算法
    // 返回删除节点后新的二分搜索树的根
    private Node remove(Node node, K key) {
        if (node == null) {
            return null;
        }
        if (key.compareTo(node.key) < 0) {
            node.left = remove(node.left, key);
            return node;
        }
        if (key.compareTo(node.key) > 0) {
            node.right = remove(node.right, key);
            return node;
        }
        // 左子树为空
        if (node.left == null) {
            Node rightNode = node.right;
            node.right = null;
            size--;
            return rightNode;
        }
        // 右子树为空
        if (node.right == null) {
            Node leftNode = node.right;
            node.left = null;
            size--;
            return leftNode;
        }
        // 左右子树均不为空
        // 删除比待删除节点大的最小节点，即待删除节点右子树的最小节点
        // 用这个节点顶替待删除节点的位置
        Node successor = minimum(node.right);
        successor.right = removeMin(node.right);
        successor.left = node.left;
        node.left = node.right = null;
        return successor;
    }


    // 返回以node为根的二分搜索树的最小值所在的节点
    private Node minimum(Node node) {
        if (node.left == null) {
            return node;
        }
        return minimum(node.left);
    }

    // 删除掉以node为根的二分搜素树中的最小节点
    // 返回删除节点后新的二分搜索树的根
    private Node removeMin(Node node) {
        if (node.left == null) {
            Node rightNode = node.right;
            node.right = null;
            size--;
            return rightNode;
        }
        node.left = removeMin(node.left);
        return node;
    }

    @Override
    public boolean contains(K key) {
        return getNode(root, key) != null;
    }

    // 返回以node为根的二分搜索树中，key所在的节点
    private Node getNode(Node node, K key) {
        if (node == null) {
            return null;
        }
        if (key.compareTo(node.key) == 0) {
            return node;
        } else if (key.compareTo(node.key) < 0) {
            return getNode(node.left, key);
        } else {
            return getNode(node.right, key);
        }
    }

    @Override
    public V get(K key) {
        Node node = getNode(root, key);
        return node == null ? null : node.value;
    }

    @Override
    public void set(K key, V newValue) {
        Node node = getNode(root, key);
        if (node == null) {
            throw new IllegalArgumentException(key + " doesn't exist!");
        }
        node.value = newValue;
    }

    @Override
    public int getSize() {
        return size;
    }

    @Override
    public boolean isEmpty() {
        return size == 0;
    }

    @Override
    public String toString() {
        res = new StringBuilder();
        inOrder();
        return res.toString();
    }

    private StringBuilder res = null;

    // 二分搜索树的中序遍历
    private void inOrder() {
        inOrder(root);
    }

    private void inOrder(Node node) {
        if (node == null) {
            return;
        }
        inOrder(node.left);
        res.append(node.key).append(":").append(node.value).append("\n");
        inOrder(node.right);
    }
}
